docs: def download_and_bootstrap(src, name, prereq=None):
      """
      Download and install something if 'prerequisite' fails
      """
      if prereq:
          prereq_cmd = '{0} -c "{1}"'.format(PY_EXE, prereq)
          rv = os.system(prereq_cmd)
          if rv == 0:
              return
  
      ulp = urllib2.urlopen(src)
      fp = open(name, "wb")
      fp.write(ulp.read())
      fp.close()
      cmdline = "{0} {1}".format(PY_EXE, name)
      rv = os.system(cmdline)
      assert rv == 0